Improving power plant flexibility – paving the way for greening the Grid

The one-day conference was jointly organised by NTPC Limited and Central Electricity Authority (CEA) and gathered a few hundred delegates from the Indian power sector, Regulator and Ministers as well as some international speakers, including myself.

India is on the growth path and additional power capacity is much needed for further development. Coal fired power plants are a significant part of the energy mix and more are being built to meet the increasing demand. However, India is also committed to lowering it carbon intensity and has an ambitious aim of 40% of non-fossil fuel capacity by 2030. This means that despite new coal power plants coming online, the proportion of coal in the country’s energy mix will decrease and coal plants will face a new challenge of increased flexibility to back up intermittent energy sources. Hence the conference was a timely event which explored possible solutions for Indian plants.

As the Minister for Power and New and Renewable Energy, R.K. Singh, and other dignitaries were present, the conference started in a grand way. India’s energy sector was described. The need of affordable and secure energy, coming both from coal and renewables, for the country’s development and future needs as well as the importance of using existing power plants in an optimal way, while lowering emissions were stressed. The necessity of increasing mining activity was also highlighted. Additionally, Minister Singh launched an online portal, E-Regn, for the registration of all existing, and under planning or in construction, grid connected electricity generating units of capacity of 0.5 MW or more. Registration is mandatory and the portal will act as a database. More on the conference inauguration can be found here.

This was followed by NTPC which highlighted different flexibility initiatives they carried out such as international collaboration in the Indio-German Energy Forum (IGEF), USAID and its studies in four power stations, and with Engie Lab, which investigates cycling costs at two stations.
The ‘Cycling requirements in Indian scenario’ session followed, and we heard from CEA, Deloitte India, GIZ/ IGEN and the Council on Energy, Environment and Water (CEEW). Mr Mallick, Chief Engineer from CEA, described the extent of flexibility required from thermal plants for five different scenarios integrating renewable energies (RES) into the grid for 2021 -22. He made it clear that the lower minimum load required in India will be around 28% and plant should not have any problems with ramping up during periods of higher demand. However, this may change in the future.

Then Mr Patnaik, Partner of Deloitte India, talked about USAID program and its various pilot tests carried out in India. These include ongoing techno-economic feasibility studies of faster ramp rates and lower technical minimum load at two NTPC units (Jhajjar and Ramagundam) and one GSEC (Ukai) unit.
Dr Damm, Head of Indo-German Energy Programme, talked about German experience of increasing the flexibility of its coal fleet and how this had become more important than efficiency gains, in the view of current energy policy.

Mr Chaturvedi, from CEEW, spoke about a high renewable energy scenario and its cost for India. He noted that current studies look 10 years ahead but there is a need for long term analysis beyond 2030 and fundamentally a different market design is imperative.

My presentation was in the second session called ‘Experience so far’ and covered how flexibility requirements may vary between different power plants, depending on markets and economics and the fact that there is no ‘one size fits all’ solution. I also described technical means for achieving common flexibility requirements for pulverised coal fired power plants and gave examples of what has been achieved so far in Europe.
Next, Mr Kendhe, Marketing and Strategy Leader, GE, shared GE’s experience and initiatives for enhancing power plant flexibility. He described the strategies that could be adopted under Indian conditions for deciding which units should be run at base load (larger units and supercritical), which ones at part load (subcritical) and which ones should be upgraded to improve efficiency.

Mr Chittora, from Siemens described how minimum technical load, higher ramps and increased plant efficiency can be achieved by a combination of various advanced process controls, component lifetime consumption monitoring, and retrofits and modernisation of the turbine and boiler. These are essential for increased flexibility but also plant profitability. Examples of plants which improved their frequency and dispatch control, and those which reduced minimum load or increased maximum load or improved their start-up while using Siemens solutions were given.

Mr Sinha from NTPC, presented the NTPC approach to increasing flexibility. He described the changes in operational practices for minimising cycling damages that can be implemented as well as the pilot tests so far.
The third session ‘Plant/equipment design futures for flexible operation’ opened with Ms Diana Daury, GE, who talked about the differences in Indian and imported coals and how burner upgrades and boiler tuning can help to stabilise combustion and lead to achieving 30 % minimum load under Indian conditions.

Mr Kim from Doosan Power Systems India described solutions for improved start-ups. The evaluation of ramp rate capacity of mechanical components is key. Several methods developed by Doosan were demonstrated on Shin Boryeong plant, South Korea, 1000 MW ultrasupercritical unit 1 and unit 2 were examples.
Mr Kakimi from L&T-MHPS Boilers, focussed on the latest burner from MHPS which is capable of stable ignition at low load (8% of boiler load, 20% of burner load) and hence allows minimum load operation.
Dr Kaminski, from STEAG, spoke about their advanced process control tool (PiT Navigator) and online lifetime monitoring as a means of power plant optimisation and improving its flexibility. Optimisation results from different plants were given including the unit heat rate improvement of 5 kcal/kWh by higher average steam temperatures and reduced RH-spray at Jharsuguda, in Odisha, India.

The last presentation was given by Mr Pande and Mr Samal form NTPC, who spoke about current load cycling specifications for new units and the design future of the turbine, steam generator and boiler for enabling flexible operation in Indian conditions. Present load cycling specifications require about 5000 start-stops and 3%/5%/min load ramp rate to which 2 cycles (minimum) of load following has recently been added. Major areas of the turbine, including rotors and casting, which are most affected by the flexible operation were discussed. For the boiler, it was highlighted that in general there is a requirement to reduce the thickness of various components, along with stress concentration. As Indian coals have a high ash content (30% or more), larger furnaces are required. The evaporator’s stability was identified as one of key areas which the NTPC’s employers must seek in their procurement specification.

As Minister Singh said ‘it is a time of change and growth in India’ and my impression is that the Indian energy sector wants to use its assets in an optimal way, while reducing their impact on the environment, and does not delay in preparing for future challenges.

‘Improving power plant flexibility – paving the way for greening the Grid’, took place 27 September 2018, at NTPC Power Management Institute, in Noida, India.